Currently, in an LTE full-duplex communications technology FDD system, user equipment receives a reference signal sent by a base station, performs channel estimation, then determines channel state information, and provides a feedback. In a process of measurement by the user equipment, a quantization loss exists. For a TDD (Time Division Duplexing, time division duplexing technology) system, uplink and downlink heterogeneousness exists in a channel. Therefore, a base station measures an uplink signal sent by user equipment, to obtain an uplink channel h, directly transposes h to obtain a downlink channel h′, and performs eigenvalue decomposition according to the downlink channel h′ to obtain a downlink precoding matrix. Therefore, by comparing FDD with TDD, for a precoding matrix of FDD, the user equipment performs measurement, and feeds back a quantized precoding matrix to the base station. Therefore, a quantization loss exists. Consequently, channel information that is fed back has an error as compared with that of TDD, resulting in lowered performance.